1. Field of the Invention
The present invention relates to a crucible for use in an electron-beam evaporator, and more particularly to a crucible that increases durability of an electron-beam evaporator to all types of materials.
2. Description of the Related Art
Typical examples of a process for manufacturing a thin film using vacuum deposition include physical vapor deposition (PVD) and chemical vapor deposition (CVD). Physical vapor deposition is classified into an evaporation process, sputtering, and ion plating.
Among the aforementioned processes, a process of manufacturing a thin film that includes evaporating materials using heat is referred to as an evaporation process or vacuum deposition in the narrow sense (vacuum deposition in the broad sense is a common designation including both PVD and CVD). Examples of an evaporation source used in the evaporation process include a resistance-heating evaporation source, an electron-beam evaporation source, and an induction-heating evaporation source.
An electron-beam evaporator includes an electron-beam evaporation source, and materials are contained in a crucible and heated using a high-voltage electron beam to evaporate them. Electron-beam evaporators have been used in various scientific experiments since the 1960s. An electron beam is advantageous in that a highly pure coat film is manufactured, evaporation materials are easily replaced, evaporation is performed at a high speed, it is easy to manufacture a multilayered film, and the manufacturing cost of evaporation materials is low.
However, since Al has a relatively low melting point but a high vaporizing temperature and very high thermal conductivity, Al is one of materials that are difficult to evaporate at a high evaporation rate using an electron beam. In consideration of this characteristic of Al, a crucible including a TiB2.BN or W material may be used. Thereby, evaporation is stably performed, but the temperature of the evaporation source is increased, wetting the crucible with Al when the power of the electron beam is increased to increase the evaporation rate, and accordingly, Al creeps along the surface of the crucible and overflows it. There are thus drawbacks in that evaporation efficiency is reduced and the crucible must be repeatedly replaced due to the aforementioned wetting phenomenon. “Evaporation Characteristics of Materials from an Electron-beam Evaporation Source” by Jae-In Jeong, et al. (Journal of The Korean Institute of Surface Engineering, Vol. 44, No. 4, 2011) discloses the evaporation characteristics of various materials and problems that occur when Al is evaporated using the known crucible.
In order to prevent the wetting phenomenon, an effort has been made to use a crucible including a ceramic material or a graphite or amorphous carbon material. However, when the crucible including the ceramic material is used, the specific resistance of the deposited Al thin film is relatively increased, and when the crucible including the graphite or amorphous carbon material is used, Al reacts with carbon at a predetermined electric power, thereby breaking the crucible.
The aforementioned characteristics serve as a problem when the Al thin film is deposited using the electron-beam evaporator on a laboratory scale, and also as a major obstacle to the industrial use of the electron-beam evaporator.